The present invention relates to a lip seal device having a lip seal in sliding contact with a rotary shaft.
A lip seal device having a case which surrounds a rotatably supported shaft and a lip seal whose inner circumferential portions are curved toward a sealed fluid and come into sliding contact with an outer circumferential surface of the rotary shaft is well known. Also as shown in Japanese Patent Unexamined Publication No.126635/1982, the lip seal device of the same type having a spiral groove formed on a seal surface between the lip seal and the rotary shaft is well known.
However, in the conventional lip seal device, there would be an undue amount of leakage of the sealed fluid because of the weakness of contact force between the lip seal and the rotary shaft particularly in the initial installed stage.
The above-mentioned lip seal device having the spiral groove arrangement is apparently inferior in sealing function to the normal lip seal device, especially when the rotary shaft is stopped.